Extract vital sign measurements from this medical document. Return a JSON array or null.

Each entry:
- type: vital type ("weight", "blood_pressure", "heart_rate", "temperature", "oxygen_saturation", "height", "head_circumference")
- value: measurement as string, e.g. "75.5"
- summary: value + unit, e.g. "75.5 kg"
- timestamp: "YYYY-MM-DD" if date mentioned
- data: {"unit": "...", "numeric_value": 75.5}

For blood pressure: value "120/80", data: {"systolic": 120, "diastolic": 80, "unit": "mmHg"}

Every entry MUST come from text explicitly present in the document. Do NOT infer or assume.
Return null if nothing relevant is explicitly described.

Document:
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